February 25, 2012

Mustard Weeds and the Curly Top Virus

Yard and Garden
February 25, 2012

Q.

I have noticed some low-growing plants that look like dandelions in my garden. When I pull them I notice a very distinct and pungent fragrance that dandelions do not produce. Is this the mustard weed that I have read about? Will it cause virus problems in my garden?

A.

You have probably identified this plant properly. Mustard weeds are low-growing, rosette plants through the winter. Their seeds sprout in the fall if there is enough moisture and they survive the winter. The fact that they are weeds competing with desired plants for water and nutrients in your garden is enough reason to identify them and remove them from the garden. However, these weeds are capable of sustaining the curly top virus through the winter in their living tissues. This virus cannot survive outside living plants. The mustard weed also harbors the beet leafhopper insect that spreads curly top virus from one infected plant to another as the leafhopper feeds on the plants.

While it is not certain that the mustard weeds contain the virus, wise gardeners begin managing this weed now by hoeing, pulling, or chemical treatments. Preventing the weeds from setting seeds by managing the problem early reduces the extent of the weed and potential virus problems in the future. Removing the weeds from the garden and in the vicinity of the garden before tomatoes, chiles, and other susceptible crops are planted is a major means of avoiding curly top virus in these crops. To learn more about curly top virus contact your local NMSU Extension Service office to obtain NMSU Extension Publication H-106 Curly Top Virus or go to http://aces.nmsu.edu/pubs/_h/h-106.html.

While you should remove the mustard from your garden, there remains a risk of curly top infection caused by insects carrying the disease from weeds off your property. Before their retirements from NMSU, Drs. George Dickerson and Ron Walser demonstrated effective management of curly top infections in tomatoes by covering the garden crops or surrounding wire cages containing the plants with spun-bonded polypropylene row cover fabric. Plants contained within the covering were much less likely to be fed upon by the beet leafhopper, and therefore, much less likely to be infected with curly top virus.

In addition to reducing curly top infection of garden plants, there are additional benefits of covering crops with row cover fabric. Plants covered in this manner are protected from the intense New Mexico sunlight and if the fabric is properly applied, the plants are protected from the infamous New Mexico spring winds. In both cases, water loss by the plants is reduced. Sunscald of developing fruit on the plants may also be reduced by row cover protection.

Mustard weeds are problems as weeds in the garden, but the greater problem is the curly top virus that they foster in the garden. Identify these weeds and remove them from your garden.